Evidence reported by retrospective investigators and our own prospective studies suggest the existence of psychological factors which precede the clinical appearance of cancer by many years. We obtain an extensive, unique data base (psychological, psychosocial, physiological, medical and familial) on a cohort of 1,337 medical students and have followed them prospectively for 18 to 32 years. Now for the most part between the ages of 41 and 60, l00 have already had some type of cancer, and all have reached the age at which the cancer incidence is rising rapidly. It is our aim: a. To study the enlarging cancer group in detail in an attempt to substantiate the youthful psychological characteristics we have already found in this cohort which appear to be potential predictors of cancer. b. To search for new potential predictors of cancer in psychological and behavioral data. c. To obtain data concerning the indicence of cancer in grandparents, parents, uncles, aunts and siblings of subjects with cancer compared with that of subjects without cancer. d. To investigate many parental attributes, psychosocial, habitual and medical, including age and cause of death, in relation to the appearance of cancer in their offspring, the former medical students. e. To determine whether special clusters of predictive variables appear to be associated with particular types of cancer.